Having diverse functions and thin designs allow mobile electronic devices such as a smart phone or a tablet computer to become mobile and versatile. However, these mobile electronic devices may become damaged as they move around from places to places. For example, the mobile electronic device may be dropped, scratched, or sat on. Consequently, relevant accessories are also vigorously developed in order to prevent mobile electronic devices from being damaged. In particular, protective accessories such as a protective casing or a protective cover are among the most popular accessories. One type of the protective casing is designed in a wallet-style or a book cover style for which the protective casing may have a cover portion that covers a display area such as the touch display screen of the tablet device to avoid damage to the display area. Similarly, for the protective cover, there would also be a cover portion to achieve similar protections.
However, the cover portion is often inconvenient to use as a user would have to open the cover portion in order to view the content of the notification in the display area when the mobile electronic devices receive a notification, For instance, when a smart phone receives an incoming call, the user would have to open the cover portion in order to view caller information displayed in the display area to decide whether to answer the call. Furthermore, users may drop the mobile electronic devices while he or she is trying to open the cover portion to view the content of the notification. Although the cover portion covers the display area to avoid damage, however, it is inconvenience for the user to operate.